1. Field of the Invention
The present invention relates to an imprint apparatus and article manufacturing method.
2. Description of the Related Art
The imprint technique is a technique capable of transferring nanoscale micropatterns, and is beginning to be put into practical use as one nanolithography technique of mass-producing magnetic storage media and next-generation semiconductor devices. In the imprint technique, a mold (template) having a micropattern is used as an original to form the micropattern on a substrate such as a silicon wafer or glass plate. More specifically, a substrate is coated with a transfer material, and the transfer material is cured while (a pattern of) a mold is pressed against the substrate with the transfer material being sandwiched between them, thereby forming a micropattern. Imprint techniques presently put into practical use are the heat cycle method and photocuring method.
Japanese Patent No. 4185941 has disclosed a technique of manufacturing semiconductor devices by using the imprint technique. In Japanese Patent No. 4185941, a pattern is formed on the entire surface of a wafer by repeating a process of forming the pattern in a partial region of the wafer. An etching process and oxidation process are performed by using the pattern formed by the imprint technique. A semiconductor device having a multilayered structure is manufactured by repeating this processing. Accordingly, the patterns must be overlaid on the same wafer, and this is the same as in the manufacture of semiconductor devices by the photolithography technique.
As an alignment technique to overlay patterns, techniques that adapt the technique for use in the manufacture of semiconductor devices by the photolithography technique are disclosed in Japanese Patent No. 4185941 and U.S. Pat. No. 7,281,921. U.S. Pat. No. 7,281,921 has disclosed a technique of monitoring the position of a mirror attached to a mold from a main body stand.
In this technique disclosed in U.S. Pat. No. 7,281,921, however, the end face of the mold must be processed to have a surface accuracy measurable by a laser interferometer and coated with a reflecting film, or a member having a reflecting surface with a high surface accuracy must be attached to the mold. Also, the reflecting surface must have a high orthogonality to two end faces among three orthogonal surfaces including a pattern surface and the two end faces. If molds are exchanged with this orthogonality being low, the normals to the two end faces cannot be aligned with the optical axis of a laser interferometer even when the rotational angle around an axis parallel to the pattern surface normal direction is adjusted (this adjustment is generally called “θ alignment”). Consequently, the path of a laser beam emitted from one laser interferometer and reflected by the end face of the mold deviates from a regular path. This makes it impossible to detect the position of the end face of the mold. Note that the surface accuracy of the reflecting surface required for a laser interferometer is generally ¼ or less the wavelength of a laser beam. For example, a laser interferometer using an ordinary He—Ne laser requires a flatness of 0.16 μm or less.
It is technically possible to provide a reflecting surface measurable by a laser interferometer on the end face of a mold. However, the number of times of use of a mold is limited because the mold deteriorates whenever a pattern is transferred. Accordingly, providing a reflecting surface measurable by a laser interferometer on the end face of a mold increases the apparatus cost and mold cost (that is, poses a serious problem in view of the cost).